1. Field of the Invention
The present invention relates to a capacitance amplifying circuit applied to a controller of a power convertor and an operation method thereof, and particularly to a capacitance amplifying circuit and an operation method thereof that can make a compensation voltage within a capacitance amplifying circuit be not continuously increased or decreased with offset and leakage of a transconductance amplifying unit when a dimming signal is disabled.
2. Description of the Prior Art
In the prior art, a controller applied to a power convertor has a compensation pin to couple to an external compensation capacitor, wherein the controller can generate a compensation voltage at the compensation pin according to the external compensation capacitor, a reference voltage, and a dimming signal, and provide the compensation voltage to a gate driving circuit within the controller. Then, the gate driving circuit within the controller can generate a gate control signal according to the compensation voltage, and output the gate control signal to a power switch of the power convertor. Thus, the power switch can be turned on and turned off to have a dimming function according to the gate control signal.
However, in highly integrated trend of integrated circuits today, the external compensation capacitor outside the controller and the compensation pin of the controller will increase cost of the controller, resulting in the controller with the external compensation capacitor and the compensation pin losing competitiveness. Therefore, how to integrate the external compensation capacitor into the controller and remove the compensation pin of the controller becomes an important issue of a designer of the controller.